Lens module including five lenses of −+++− refractive powers, and electronic device using the same

Abstract

A lens module includes a first lens having a negative refractive power, a second lens having a positive refractive power, a third lens having a positive refractive power, a fourth lens having a positive refractive power, a fifth lens having a negative refractive power, and an imaging surface, arranged in that sequence from an object side to an image side. The lens module uses infrared light which has a wavelength ranging from 920 to 970 nm, the lens module satisfies the following conditions: 0.0002<|1/F1|<0.01; D/TTL>1.1; CT4/ET4<1.8; F1 denotes a focal length of the first lens, D denotes a diameter of a largest imaging circle of the lens module, TTL denotes a distance between an object side surface of the first lens to the imaging surface, CT4 denotes a central thickness of the fourth lens, ET4 denotes an edge thickness of the fourth lens.

What is claimed is: 
     
       1. A lens module, wherein the lens module is operable with infrared light which has a wavelength ranging from 920 to 970 nm, the lens module substantially consisting of:
 a first lens having a negative refractive power; 
 a second lens having a positive refractive power; 
 a third lens having a positive refractive power; 
 a fourth lens having a positive refractive power; 
 a fifth lens having a negative refractive power; and 
 an imaging surface, wherein the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are arranged in that sequence from an object side to an image side, the lens module satisfies the following conditions:
   0.0002<|1/ F 1|<0.01; 
     D/TTL> 1.1; 
     CT 4/ ET 4<1.8; 
 
 wherein, F1 denotes a focal length of the first lens, D denotes a diameter of a largest imaging circle of the lens module, TTL denotes a distance between an object side surface of the first lens to the imaging surface, CT4 denotes a central thickness of the fourth lens, ET4 denotes an edge thickness of the fourth lens. 
 
     
     
       2. The lens module of  claim 1 , wherein the first lens comprises a first surface facing the object side and a second surface facing the image side, the second lens comprises a third surface facing the object side and a fourth surface facing the image side, the third lens comprises a fifth surface facing the object side and a sixth surface facing the image side, the fourth lens comprises a seventh surface facing the object side and a eighth surface facing the image side, the fifth lens comprises a ninth surface facing the object side and a tenth surface facing the image side, each of the first to the tenth surfaces is an aspherical surface. 
     
     
       3. The lens module of  claim 2 , wherein the first surface is concave on the object side, the second surface is convex on the image side, the third surface is convex on the object side, the fourth surface is convex on the image side, the fifth surface is concave on the object side, the sixth surface is convex on the image side, the seventh surface is concave on the object side, the eighth surface is convex on the image side, the ninth surface is convex on the object side, the tenth surface is concave on the image side. 
     
     
       4. The lens module of  claim 2 , wherein the lens module further satisfies the following conditions:
   0<|1/ F 1|<|1/ F 3|<|1/ F 4|; 
 
       wherein F3 and F4 respectively denotes focal lengths of the third lens and the fourth lens. 
     
     
       5. The lens module of  claim 2 , wherein the lens module further satisfies the following conditions:
   | G 5 R 1/ F 5|>| G 5 R 2/ F 5|>0; 
 wherein G5R1 denotes a radius of curvature of the ninth surface, G5R2 denotes a radius of curvature of the tenth surface, and F5 denotes a focal length of the fifth lens. 
 
     
     
       6. The lens module of  claim 2 , wherein the lens module further satisfies the following conditions:
   0< G 1 R 1/ F 1<0.03, 0< G 1 R 2/ F 1<0.03; 
   0.3< G 2 R 1/ F 2<1, 2< G 2 R 2/ F 2<3; 
   −5< G 3 R 1/ F 3<−3, −1< G 3 R 2/ F 3<0;
 
   −0.7< G 4 R 1/ F 4<−0.3, −0.5< G 4 R 2/ F 4<−0.2;
 
   −1< G 5 R 1/ F 5<−0.5, −0.4< G 5 R 2/ F 5<−0.1;
 
 
       wherein G1R1, G1R2, G2R1, G2R2, G3R1, G3R2, G4R1, and G4R2 are respectively denotes radiuses of curvature of the first surface, the second surface, the third surface, the fourth surface, the fifth surface, the sixth surface, the seventh surface, and the eighth surface. 
     
     
       7. The lens module of  claim 2 , further comprising a filter arranged between the fifth lens and the imaging surface. 
     
     
       8. An electronic device comprising:
 a lens module, wherein the lens module is operable with infrared light which has a wavelength ranging from 920 to 970 nm, substantially consisting of: 
 a first lens having a negative refractive power; 
 a second lens having a positive refractive power; 
 a third lens having a positive refractive power; 
 a fourth lens having a positive refractive power; 
 a fifth lens having a negative refractive power; and 
 an imaging surface, wherein the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are arranged in that sequence from an object side to an image side, the lens module uses infrared light which has a wavelength ranging from 920 to 970 nm, the lens module satisfies the following conditions:
   0.0002<|1/ F 1|<0.01; 
     D/TTL> 1.1; 
     CT 4/ ET 4<1.8; 
 
 wherein, F1 denotes a focal length of the first lens, D denotes a diameter of a largest imaging circle of the lens module, TTL denotes a distance between an object side surface of the first lens to the imaging surface, CT4 denotes a central thickness of the fourth lens, ET4 denotes an edge thickness of the fourth lens. 
 
     
     
       9. The electronic device of  claim 8 , wherein the first lens comprises a first surface facing the object side and a second surface facing the image side, the second lens comprises a third surface facing the object side and a fourth surface facing the image side, the third lens comprises a fifth surface facing the object side and a sixth surface facing the image side, the fourth lens comprises a seventh surface facing the object side and a eighth surface facing the image side, the fifth lens comprises a ninth surface facing the object side and a tenth surface facing the image side, each of the first to the tenth surfaces is an aspherical surface. 
     
     
       10. The electronic device of  claim 9 , wherein the first surface is concave on the object side, the second surface is convex on the image side, the third surface is convex on the object side, the fourth surface is convex on the image side, the fifth surface is concave on the object side, the sixth surface is convex on the image side, the seventh surface is concave on the object side, the eighth surface is convex on the image side, the ninth surface is convex on the object side, the tenth surface is concave on the image side. 
     
     
       11. The electronic device of  claim 9 , wherein the lens module further satisfies the following conditions:
   0<|1/ F 1|<|1/ F 3|<|1/ F 4|; 
 
       wherein F3 and F4 respectively denotes focal lengths of the third lens and the fourth lens. 
     
     
       12. The electronic device of  claim 9 , wherein the lens module further satisfies the following conditions:
   | G 5 R 1/ F 5|>| G 5 R 2/ F 5|>0; 
 
       wherein G5R1 denotes a radius of curvature of the ninth surface, G5R2 denotes a radius of curvature of the tenth surface, and F5 denotes a focal length of the fifth lens. 
     
     
       13. The electronic device of  claim 9 , wherein the lens module further satisfies the following conditions:
   0< G 1 R 1/ F 1<0.03, 0< G 1 R 2/ F 1<0.03; 
   0.3< G 2 R 1/ F 2<1, 2< G 2 R 2/ F 2<3; 
   −5< G 3 R 1/ F 3<−3, −1< G 3 R 2/ F 3<0;
 
   −0.7< G 4 R 1/ F 4<−0.3, −0.5< G 4 R 2/ F 4<−0.2;
 
   −1< G 5 R 1/ F 5<−0.5, −0.4< G 5 R 2/ F 5<−0.1;
 
 
       wherein G1R1, G1R2, G2R1, G2R2, G3R1, G3R2, G4R1, and G4R2 are respectively denotes radiuses of curvature of the first surface, the second surface, the third surface, the fourth surface, the fifth surface, the sixth surface, the seventh surface, and the eighth surface. 
     
     
       14. The electronic device of  claim 9 , wherein the lens module further comprises a filter arranged between the fifth lens and the imaging surface.